Communication system



Aug. 4, 1931. J. w. HoRToN 1,816,905

COMMUNICATION SYSTEM Filed Feb. 21, 1929 2 Sheets-Sheet l A TURA/EY Aug. 4, 1931.

FREQUENCY J. W. HORTCN COMMUNICATION SYSTEM Filed Feb. 21, 1929 2 Sheets-Sheet 2 L/. W HUH 70N Patented Aug. 4, 1931 `".UisirsoSTATES PATENT OFFICE ,'I'SEIVEH` W. HORTON, OF CAMBRIDGE, MASSACHUSETTS, ASSIGNOR T0 `:BELL TELE- y PHONE LABORATORTES, 1N CORPORATED, 0F NEW YORK, N. Y., A CCRPOR-ATION 0F i NEW YORK COMMUNICATION SYSTEM iuApplicvaton filed February 21, 1929.` Serial No. 341,597.

Y This invention relates to communication systems and more particularly toa system in which .individual or simultaneous communication with a selected group of'stations may 5 be had.

An object of the invention'is to permita group of stations on a power line or other transmission line to. communicate with a master station individually to the exclusion of one 'another or forthe master station to Y communicate with onegtwo or kany number of the other stations in any combination.

A feature of the invention resides in using band pass filters capable of passing different portions of the frequency spectrum, at difierent stations of a group connected to a power line or the like. The bands of frequencies passed by the filters at th'erespective stations partially overlap in a predetermined manner to permit communication between the master station and the linestations in the combinations above set forth. A better understanding of the invention may bev had by readingthe following descrip- 2.5 tion together with'the accompanying drawings, of which Figs. l and 1A when placed `yside by side represent a power lineor other type of transmissionlineto which a master station may be connected for communicating with a plurality of stations placed at intervals along the line, and Fig. 2, a diagramof the transmission ranges of the filters used at the various stations.

' In Figs. iand 1A, a system is shown in whichr a master station may communicate with three stations,X, Y and Z connected at 'intervals along a power line L or the like, individually or in any desired combination. VIn order to provide for this type of service 40 `with'vthree stations, it is necessary to have seven different frequency channels at the master station. The manner' in which selectivity is obtained at the various substations is shown by referring to the filter characteristics in Fig. 2. From this figure, it may be -seen that the band pass filter F, includes three of the frequency bands atfthe master Stationmamely bands 1, 2 and 3.

The band-pass filter F'c isdisplaced one band fromFaand includes bands 2, 3 and 4.

The filter Feisdisplaced one band from Fc and transmits four bands, namely, 3, 4, 5 and 6. A fourth filter F b transmits one band 6, in common with filter Fc, while ranother filter Fd transmits band 7 exclusively.

It can now be seen that by placing two kfilters Fa and Fb at station X, filters F c and F d at station Y and F e at station Z, the master station may communicate with station X to the exclusion of stations Y and Z by using the frequency band 1, with station Y to the exclusion of stations X and Z by using the frequency band 7 and with station Z to the exclusion of the stations X and Yfby using the frequency band 5, since these bands are passed exclusively by filters at these stations, respectively. By using the frequency band 2, the master station may communicate with stations X and Y to the exclusion of station Z, since this band is common to filters Fa at station X and F C at station Y. Similarly the master station may communicate with stations Y and Z to the exclusion of station X by using the band t which is common to the filters Fe and Fc located respectively at over this band if proper sending means arey located at these stations and provision made for differentiating' and receiving incoming signals at the master station.

The master station is associated with the line L through the hybrid coil 13 which together with the balancing network Maids in separating the incoming and outgoing signals in well-known manner. The sending apparatus at the master station comprises an oscillator 10 which may be of any well-known type, as for instance, that disclosed in Patent 1,356,763 to R. V. L. Hartley, issued October 2.6', 1920, and a modulator 12 in Which vthe A carri-er frequency from the oscillator is Inod- 'ployed ulated With the signaling frequencyvfrom vthe microphone 11 toproduce a band for transmission to the stations'. f Y

'Y A pluralitylof frequency determining` circuits 1 to` .7 are associated With the oscillator, one `only Vof which, as determined by the frevquency banddesired to. 'be used, is connected, With the oscillator at one time.

Four of thesev circuits, namely, 2, 3, 4 and 6 are emand '7, are employed in connectionjvith the channels for two-Way communication'of the master Ystation With the individualY stations.

-ArV plurality of jacks 33 to 39 are provided whereby the desired,selectingfcailing and answering of the various stationsmaybe acy rc'oinp'lish-ed and the proper frequenrydetermining circuits maybe associated with the` oscillator.` 'Four of the jacks, namely, 33 to 36,` are used in calling line stations from the master station. These jat-us have tivo pairs of contacts for connecting afrequency deter-- mining circuit to the oscillator andv a'sour-ce of energy to the oscillator. 'For instance, if it is desired to call stations X and Z, a plug 44 is inserted in the ack 33, which connects the frequency determining circuit 6 lto the Y oscillator. This completes the circuit vfrom the ground at 37 through the battery 33, 'lead 45,` plug' 44, lead 46 and the relay 41 to ground. Upon completion of "this circu1t ,the

` relay A'41' attracts its armature to completen circuit from the Vsource of electrical energy 471Which supplies current to the filamentvk of the oscillator.r At the Sametime, a vcircuit is completed from -the'oscillator through `the frequency determining circuit 6, contacts '42 ofthe Iiack 33, through thelead 43, Vback to the oscillator. Similarly, in initiating other calls, by plugging in the jacks 36, 35 and respectively, frequency determini-ng circuits 2, and 4 are connected tothe oscillator.V

The jacks 37 tcf39 having an yextra'pair-of contacts are answering' jacks andare similarlyassociated With the frequency'determining circuitsv '1,' 5V` and 7" employed in the' two-Way channels. The additional vpairs eff'contacts CLL enable a receiving device Which ma f beV av loud speaker 31 and a detector 30 to be connectedwto the incomingbranches ofthev tivo- Way' channels.Y las mentioned'above, three -band passjfilt'ers, namely, El', "Fg andi?T each of which passesone of thebands of 'frequencies that Ia line station has exclusively incomkmonivith the master station, are provided Vto differentiate' between the incoming signals. 'Associated With each of these incoming pathsv "isarelay device 24, 25 or 26 Whichoperates togive a signalito an attendant to indicate f which of the .line stations is calling. .These indlcating signals 'may be 'lamps 2T, 28 vand in onen-way communication to the stations in various combinations as heretofore described, While three ofthem, namely, 1,0v

29 asociated With the relay circuits or any other'type of indicating means which it may be desired toV use. When the plug 32 is inserted in one of the jacks as for instance 39,

a through circuit is provided from the station X to the receiver 31. At the same time contacts 48 and 49 are closed, connecting the frequency determining circuit 1 to the oscillator andfcompleting the circuit through the relay` 41 Ywhich operates to energize the oscillator.

Since the line L may be a power line or the lilre,ja vhigh pass filter 15 is provided Which readilygpas'ses the signaling bands but excludes the low frequency power from the signaling circuits, While at the same .time-a low pass filter 16 lexcludes ythe :signaling currents from A:the power apparatus, or otherloW-frequency circuits that may beassociated With line L. v

kThe band passV lilters Fa and Fb .at station l' X, F'cand FdV at station Yand Feat station Z in .addition rto determining the frequency bands which are transmittedito and from lthe line stations `also exclude the vflow frequency power inthe line L Yfromthe signaling circuits. Each line stationisrequipped with a hybridV coil 17 ysimilar to that yat A.the master station to aid inseparating lfthe incoming and outgoing signals. Sending and ireceivf -master station; Thus the l.sending frequency Aat station X 1s mthefrequency banddthat I at lstation-Y `in l.the frequency band fr', 'and that lat 'station' Z in the frequency .band-5.

In order to'operate the system, the attend yant-iat the :master station determines which of the stations'orv 'combination of 'stationshe desires 'to communicatewith. He thenfplugs into the jack Whichvvill cause ithe oscillator to generate the frecpiency, which ifs'iin fthe channelth'a't is exclusive 'tofthat station or group of stations. The signals from .themii crophone 11 modulatelrthe carrier @requency generated by the oscillator'lO vto produce a nos band which is 'transmittedto and detected atthe stations, as determined by the fband filter located thereat.

If the attendant at one ofthe line stations desires to -communicatefivith the master -station, the oscillator `thereat ywhichh'as a Vfrequency in a band excludedfroiu thev'other line stations is started. 'This 'frequency -is transmitted to the master station Where it is directed into its proper channel by one'of the band pass lilters F1, F5 Vor 7; The signal lamp associated 'With that channel operates and indicates to the attendant at themaster station Which of the line stations is calling. The receiving apparatus is plugged into the proper jack, starting the oscillator l0 Which generates Waves oit the same frequency as those at the line stations. he system is then in condition for two-Way operation with this station.

For instance, if the attendant at the ystation X desires to call the master station he closes a'switch which may be arranged to Y start the oscillator 2l as Well as to connect the Y frequency determining circuit lV thereto.

The freffuency generated is transmitted to the master station Where it is selectively passed by the ilter F1 to operate the signal lamp 27, thus apprising the attendant at the master station that station X is calling, The

c attendant at the master station inserts the plug 32 in the answering` jack 39 thereby permitting the signals from station X to be received and at the same time starting the oscillator lOYat the frequency Which permits eX- clusive communication with station X. When the attendant at the latter station receives an answer Jfrom the master station he is aware that he may proceed to communicate With it.

Although two or more of the stations may desire to communicate With the master station simultaneously, interference is prevented at the master station by the attendant who has it in his power to select the station with which he desires to communicate. However, the fact that other stations are attempting to communicate With the master station is indicated to the attendant by means of the sig'- nal llamps associated with those channels so that upon the termination of the conversation With vone station, another staitonv may be picked up by plugging into its associated jack.

Although this invention has been described in connection With one specific embodiment and a limited number of stations, nevertheless it is capable of broad interpretation and application to many stations, and is to be limited therefore only by the scope of the appended claims. n

lVhat is claimed is:

l. In a communication system, means for communicating with a plurality of stations in different combinations, and means con prising iilters having overlapping transmissionV bands for' determining said combinations. l

2. In a communication system, means tor transmitting signals over a. line in a plurality of signal channels, receiving means connected at intervals along said line, and different selective circuits associated with each oit said receiving means having in part common and in part individual frequency ranges, all of said selective circuits aiding to permit simultaneous reception at various combinations of said stations, and exclusive reception at each one thereof individually.

3. In a communication system, means for transmitting signals over a line in a plurality of signal channels, receiving stations connected at intervals along said line, and a plurality ot' selective circuits having overlapping transmission bands distributed among said stations for enabling selective communication with said stations singly or in groups.

4. In a transmission system, a transmission line, means for providing a plurality of signal channels for transmitting signals over said line, receivingl stations connected at intervals along said line, selective means at each of said stations for communicating over' different groups of said channels, some of which channels are common to certainoi said selective means and individual to others, and means for communicating exclusively With saidstations or with any combination oi' them as determined by the transmitting channel selected.

5. In a transmission system, a transmission line, a master station connected thereto for transmitting signals to a plurality ot' stations along the line, means at said master station for providing a plurality of signaling channels, filtering means at said line stations for permitting communication over some of said signal channels but not over others, said filters having transmission ranges partially overlapping so that each station may receive in a channel exclusive to itself or in common With the others, individually or in any combination, the station or combination of stations receiving signals being determined by the channel selected for use at said master station.

6. In combination a transmission line, amaster station connected thereto foi-transmitting signals to a plurality of stations along the line, a. plurality of carrier channels at said master station, means for generating carrier frequencies tor communicating in each of said carrier channels, means for modulating said carrier frequency signals to produce a plurality of frequency bands, receiving means connected at said master and said line stations, a plurality of band-pass ilters at said line stations, each of said stations having a portion of the transmission region of its filter means capable ot transmitting the signal band from one channel to the exclusion of the otherl stations, one portion capable of transmitting a signal band from another channel in common with all of said stations, and other portions capable ot transmitting a signal band from still other channels common to one each ol the oher stations, and transmitting means at each of said line stations for communicating with CFI theinaster station `.Within its exclusive frequency band. Y l Y 7. In combination, a transmission line, a

master station connected thereto tor transmitting signals to a pluiality of stations, transmitting and receiving means at said stations, means at said master station .for transmitting in a pluralityof channels, said means comprising an oscillatoirand a plurality of frequency determining circuits, meansV at each of said linestations for communicating Withzsaid master station in a diiiei-ent one of said channels, diiierent'combinations of said stations being capable also `of receiving signals from said master station in other ot said channels, band-pass'ifilters at said line stations having transmission bands passing signals from dilereni groups of said channels, theV signals from some of said channels, however, being received incommonby said stations, and meansat said master station for selecting the signaling channel which permits transmission to the 4desired station or combination of stations. V

.8. ln a communicating system, a master station and a. plurality of lineV stations, individual two-way signaling channels associated vtherewith for permitting' exclusive communication between ysaid Ymaster station and each oitv said' line stations, one-Way signaling channels also associated with said stations for permitting the simultaneous communication of said vmaster station vWith all of said stations or any combination thereof,

Vfiltering means at each ot said line stations for exclusively transmitting signals in one oi: said two-Way channels, said means also transmittinmsiiials in a channelconiinon' tok all o'said other stations, and signals in separate channels commento each one votsaid otherstatioiis.` y y 9111i arcommunication system, a master station and a plurality of line stations, in-` K dividual tivo-Way signaling channels associated.V therewithrv tor permitting exclusive -coi'nmiinication between said master station and each of said line stations, one-Way signaling channels also associated with said stations for Vpermitting the simultaneous'communication of said master station Withall Y oi' said stations or any combination thereof,

filtering-,means at said master station for difierentiating between the incoming signals in said two-Way channels, indicating meansv at vsaijdf'master station associated'ivith the insion means at the master station for alllSWerileY ,comingV channels tor indicating When said Channels are iii'operation, andliltering means :eachrofsaid lineestations for exclusively passing signals in one oit` said two-Way chiannels, said means also passing signals in a channel common with all of saidothei stations .and signals in separate channels coinmon to Aeacli one of said other stations.

10'. A 'communication system in: accordance with claim 9 in which ine'ansrare pro- 

